Blood is making a comeback in neuroscience and psychology research. Centuries ago, Galen thought that personality and behavior were governed by the four “humors” with blood being one of them. A few months ago, blood gained some credibility in neuroscience when a study published in Nature found that the donation of blood collected from a young mouse to an old mouse forestalled neurodegeneration while donation of blood collected from an old mouse to a young mouse accelerated neurodegenetaion. Read the full details in this blog post.
As for how the blood may carry sleep-promoting factors that cross the brain and act on sleep regulatory areas, there may be a few. Recently, researchers at UPENN have undertaken an extensive study where they collected the blood from individuals sensitive or resistant to sleep deprivation. The researchers deprived the subjects of sleep for 38 hours and figured out just how sensitive or resistant the subjects were to sleep deprivation through a simple, reliable test of mental alertness and lapses: the psychomotor vigilance test. Performance on the PVT was compared against the blood genome of these individuals. The results were striking in that it pointed out that most of the genes were more sensitive to time-of-day, a circadian effect, rather than the environment challenge of sleep deprivation, a homeostatic effect. Separating circadian and homeostatic influences on daily sleep amounts is a constant struggle. In this study, the researchers were able to identify circadian vs. homeostatic influences without even controlling for these processes through a unique protocol called forced desynchrony. There were two genes that showed sensitivity to sleep loss in that their gene expression increased across a protocol of sleep deprivation, but for the most part, the genes peaked in the mid-night or mid-day which conveniently correspond with biologically driven dips in core body temperature. However, the rhythms of this waxing and waning of gene expression was dampened in the lucky bastards who are resistant to changes in mental performance with sleep deprivation.
And so while this study has narrowed down some possibilities, the quest for a single, peripheral regulator of sleep centers in the brain continues. Hopefully I am the first to find it.
Arnardottir, E., Nikonova, E., Shockley, K., Podtelezhnikov, A., Anafi, R., Tanis, K., Maislin, G., Stone, D., Renger, J., Winrow, C., & Pack, A. (2014). Blood-Gene Expression Reveals Reduced Circadian Rhythmicity in Individuals Resistant to Sleep Deprivation SLEEP DOI: 10.5665/sleep.4064